U.S. Pat. No. 3,830,233, owned by the assignee of the present application, discloses a therapeutic device which is designed to apply periodically a controlled amount of traction to a human body. The device includes a table having a top which reciprocates lengthwise to move a patient lengthwise in the course of treatment. A traction applicator unit mounted at one end of the table has an arm which projects upwardly and which is adapted to be coupled at its upper end to a harness connected to the patient lying on the table. The arm is connected to a brake drum by a ratchet mechanism which causes the brake drum to rotate unidirectionally each time the arm is pivoted as the table moves the patient away from the traction unit. The magnitude of the traction applied to the patient is controlled by a brake shoe which surrounds the drum and which is connected to an adjustment mechanism.
U.S. Pat. No. 2,882,805 and U.S. Pat. No. 2,781,040, both owned by the assignee of the present application, also disclose therapeutic tables of similar construction.
While the aforementioned patented treatment tables function satisfactorily for their intended purposes, there is a need for certain improvements. For instance, while the traction adjusting mechanism is calibrated at the factory prior to shipment, the user must frequently calibrate the mechanism in order to insure the application of an accurate amount of traction to the patient. This is due to the tendency of the brake shoe to wear over a period of time. Brake shoe wear induces error in the traction adjustment settings. To maintain accuracy in the adjustment settings, the unit is calibrated by connecting a spring scale to the arm and pulling on the scale to pivot the arm and thereby to measure the tension applied for a given setting of the adjustment mechanism. Thereafter, appropriate notations are made on the scale of the adjustment mechanism to correct for the error induced as a result of brake shoe wear. Needless to say, this procedure is time consuming and, therefore, undesirable.